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Subject: Re: [PATCH v6 05/13] arm64: Don't trap host pointer auth use to EL2
To:     Kristina Martsenko <kristina.martsenko@arm.com>,
        linux-arm-kernel@lists.infradead.org
Cc:     Adam Wallis <awallis@codeaurora.org>,
        Amit Kachhap <amit.kachhap@arm.com>,
        Andrew Jones <drjones@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christoffer Dall <christoffer.dall@arm.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Dave P Martin <dave.martin@arm.com>,
        Jacob Bramley <jacob.bramley@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
References: <20181207183931.4285-1-kristina.martsenko@arm.com>
 <20181207183931.4285-6-kristina.martsenko@arm.com>
From:   Richard Henderson <richard.henderson@linaro.org>
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Date:   Sun, 9 Dec 2018 08:54:44 -0600
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On 12/7/18 12:39 PM, Kristina Martsenko wrote:
> From: Mark Rutland <mark.rutland@arm.com>
> 
> To allow EL0 (and/or EL1) to use pointer authentication functionality,
> we must ensure that pointer authentication instructions and accesses to
> pointer authentication keys are not trapped to EL2.
> 
> This patch ensures that HCR_EL2 is configured appropriately when the
> kernel is booted at EL2. For non-VHE kernels we set HCR_EL2.{API,APK},
> ensuring that EL1 can access keys and permit EL0 use of instructions.
> For VHE kernels host EL0 (TGE && E2H) is unaffected by these settings,
> and it doesn't matter how we configure HCR_EL2.{API,APK}, so we don't
> bother setting them.
> 
> This does not enable support for KVM guests, since KVM manages HCR_EL2
> itself when running VMs.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
> Acked-by: Christoffer Dall <christoffer.dall@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: kvmarm@lists.cs.columbia.edu
> ---
>  arch/arm64/include/asm/kvm_arm.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


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